Mac 10.8.5 で VMWare Fusion 6 を実行しています。vagrant-vmware-fusion プラグインをインストールしようとしたところ、このエラーが発生しました。これは Ruby の問題だと思いますが、Ruby を使った経験がないのでよくわかりません。どんな助けでも大歓迎です。
vagrant plugin install vagrant-vmware-fusion
Installing the 'vagrant-vmware-fusion' plugin. This can take a few minutes...
/Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader/entry.rb:127:in `read': undefined method `size' for nil:NilClass (NoMethodError)
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader/entry.rb:126:in `read'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader/entry.rb:126:in `read'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/format.rb:73:in `block (2 levels) in from_io'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:64:in `block in each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:55:in `loop'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:55:in `each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_input.rb:138:in `block (2 levels) in each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:28:in `new'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_input.rb:137:in `block in each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:64:in `block in each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:55:in `loop'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_reader.rb:55:in `each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_input.rb:132:in `each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/format.rb:66:in `block in from_io'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package/tar_input.rb:22:in `open'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/package.rb:44:in `open'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/format.rb:62:in `from_io'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/format.rb:46:in `block in from_file_by_path'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/format.rb:45:in `open'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/format.rb:45:in `from_file_by_path'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/installer.rb:119:in `format'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/installer.rb:129:in `spec'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/installer.rb:386:in `ensure_required_ruby_version_met'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/installer.rb:156:in `install'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/dependency_installer.rb:297:in `block in install'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/dependency_installer.rb:270:in `each'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/dependency_installer.rb:270:in `each_with_index'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/dependency_installer.rb:270:in `install'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/action/install_gem.rb:49:in `block in call'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/gem_helper.rb:42:in `block in with_environment'
from /Applications/Vagrant/embedded/lib/ruby/1.9.1/rubygems/user_interaction.rb:40:in `use_ui'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/gem_helper.rb:41:in `with_environment'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/action/install_gem.rb:39:in `call'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/action/warden.rb:34:in `call'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/action/bundler_check.rb:20:in `call'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/action/warden.rb:34:in `call'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/action/builder.rb:116:in `call'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/action/runner.rb:61:in `block in run'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/util/busy.rb:19:in `busy'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/action/runner.rb:61:in `run'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/command/base.rb:17:in `action'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/command/install.rb:27:in `execute'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/plugins/commands/plugin/command/root.rb:52:in `execute'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/cli.rb:38:in `execute'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/lib/vagrant/environment.rb:478:in `cli'
from /Applications/Vagrant/embedded/gems/gems/vagrant-1.3.5/bin/vagrant:96:in `<top (required)>'
from /Applications/Vagrant/bin/../embedded/gems/bin/vagrant:23:in `load'
from /Applications/Vagrant/bin/../embedded/gems/bin/vagrant:23:in `<main>'